Protesters throw stones at police during a general strike against a pension reform measure, outside Congress in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Victor R. Caivano)

Protesters clash with police during a general strike against a pension reform measure, outside Congress in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Victor R. Caivano)

Protesters throwing stones at police are sprayed by water cannons during a general strike against a pension reform measure, outside Congress in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Victor R. Caivano)

A demonstrator throws a stick at police during a general strike against a pension reform measure in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Natacha Pisarenko)

Protesters topple fences that block them from reaching Congress, behind, as they clash with police during a general strike against a pension reform measure in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Victor R. Caivano)

A woman is assisted by a doctor after clashes between demonstrators and police during a general strike against a pension reform measure, outside Congress in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Natacha Pisarenko)

Police block protesters along a road leading to the Congress, behind, during a general strike against a pension reform measure, outside Congress in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Victor R. Caivano)

Protesters build a makeshift wall to shield themselves from rubber bullets fired by police during a general strike against a pension reform measure, outside Congress in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Victor R. Caivano)

A police officer fires rubber bullets at demonstrators during a general strike against a pension reform measure in Buenos Aires, Argentina, Monday, Dec. 18, 2017. Union leaders complain the legislation, which already passed in the Senate, would cut pension and retirement payments as well as aid for some of poor families. (AP Photo/Natacha Pisarenko)

Demonstrators threw bottles, rocks and gasoline bombs, while police in riot gear responded with tear gas, rubber bullets and jets of water. Authorities said 48 people had been arrested and 149 were injured, including police officers, retirees and journalists.

"We have no one to defend us," said 70-year-old Cristina Sanmero, who found herself caught in the clashes. "At my age, I have to come here and defend my contributions of 30 years. We're governed by inept people who think that it's easier to take away from the old."

The measure, which already passed the Senate, is part of a series of economic changes pushed by the government of President Mauricio Macri to reduce the government's high deficit. Union leaders and social activists complain the legislation would cut pension and retirement payments as well as aid for some poor families.

Argentina's largest union began a 24-hour general strike at noon Monday to protest the bill, which was being debated in the lower Chamber of Deputies. Hundreds of airline flights were grounded in the Argentine capital due to the stoppage.

A debate on the measure was suspended Thursday due to similar violent clashes.

The government later amended the proposal to include a bonus payment for some retirees. But critics said it was not enough.

"The bonus payment is a joke," said Juan Carlos Schmid, a leader of the CGT union. The measure "is illegitimate and will cause a waterfall of lawsuits against it."

Demonstrators in several neighborhoods of Buenos Aires banged on pots Monday night to protest the measure. The protests hold deep symbolism for Argentines, who recall the country's worst economic crisis in 2001-2002, when pot-banging marches forced presidents from office.

Since taking office in 2015, Macri has vowed to rein in government spending and revive Argentina's lagging economy. But his ordering of job cuts and the cutting of utility subsidies has fueled labor unrest.

In October, the conservative leader announced that he would seek more sweeping changes in tax, education and labor after his governing coalition scored a resounding victory in congressional elections.